mud flapper
A persons asshole.
Guy# 1: Holy shit ....did you see the turd left in the toilet from Larry? Guy# 2: Hand me the plunger and a knife. He's got a big mud flapper to drop something like that!
Mississippi Mud-Flapper
When a guy shits in a girls vagina then proceeds to eat her out.
Dude...she wanted to do a Mississippi Mud-Flapper last night and it went all over the wall